Systems and methods for reducing banding artefacts of an image on a substrate

Abstract

Scan printing systems and methods for reducing banding artifacts of an image printed on a substrate, including a substrate feeder assembly, a printhead adapted to print an encoder pattern on the substrate, a sensor, and a controller. The controller performs a feedback cycle of positioning the substrate relative to the printhead and instructs the printhead to print a band of the image when the encoder pattern has reached a target position. The controller repeats the feedback cycle of positioning the substrate relative to the printhead and instructs the printhead to print a subsequent band of the image until the entire image is printed on the substrate.

The invention claimed is: 
     
       1. A scan printing system for reducing banding artefacts of an image printed on a substrate, the scan printing system comprising:
 a substrate feeder assembly adapted to move the substrate along a substrate moving path; 
 a printing assembly configured to receive image data and including a printhead adapted to print an encoder pattern and a band of the image on the substrate; 
 a sensor configured to detect the encoder pattern on the substrate; and 
 a controller coupled to the substrate feeder assembly, the printhead, and the sensor, and the controller configured to receive position data of the encoder pattern from the sensor and determine a target position for the substrate along the substrate moving path; 
 wherein the controller initiates printing of the image by instructing the printhead to print an encoder pattern and a band of the image on the substrate; 
 wherein the controller performs a feedback cycle for positioning the substrate relative to the printhead, the feedback cycle including
 calculating a projected moving distance for the encoder pattern to move along the substrate moving path to reach the target position, 
 directing the substrate feeder assembly to move the substrate over the projected moving distance, 
 receiving new position data of the encoder pattern from the sensor, 
 determining whether the encoder pattern has reached the target position based on the new position data, and 
 repeating the feedback cycle until the encoder pattern reaches the target position; 
 
 wherein the controller instructs the printhead to print another encoder pattern and another band of the image when the encoder pattern has reached the target position; 
 wherein the controller repeats the feedback cycle of positioning the substrate relative to the printhead until the another encoder pattern reaches a subsequent target position; 
 wherein the controller continues with instructing the printhead to print another encoder pattern and another band on the substrate and repeating the feedback cycle for positioning the substrate relative to the printhead until the desired image is printed on the substrate; and 
 wherein the encoder pattern includes a leading object and a lagging object, and wherein the controller calculates the target position based on a distance between the leading object and the lagging object, a width of the printhead, and a scalar value determined by the number of passes used to print each band. 
 
     
     
       2. The scan printing system of  claim 1 , wherein the encoder pattern includes a plurality of objects. 
     
     
       3. The scan printing system of  claim 2 , wherein positions of the plurality of objects are mapped onto an image array of the sensor to calculate the target position and the projected moving distance of the substrate. 
     
     
       4. The scan printing system of  claim 1 , wherein the encoder pattern is printed on the substrate in an area outside of the printed band. 
     
     
       5. The scan printing system of  claim 1 , wherein the encoder pattern is part of the band of the image on the substrate. 
     
     
       6. The scan printing system of  claim 1 , wherein the encoder pattern includes magnetic marks. 
     
     
       7. The scan printing system of  claim 1 , wherein the encoder pattern includes electrically conductive marks. 
     
     
       8. A scan printing method for reducing banding artefacts of an image on a substrate, the method comprising:
 (a) printing an encoder pattern on the substrate; 
 (b) detecting the encoder pattern with a sensor; 
 (c) determining a target position based on position data of the encoder pattern; 
 (d) calculating a projected moving distance of the substrate to reach the target position; 
 (e) moving the substrate by the projected moving distance; 
 (f) detecting a new position of the encoder pattern with the sensor and determining whether the encoder pattern has reached the target position; 
 (g) repeating steps (d)-(f) until the encoder pattern reaches the target position; 
 (h) printing a band of the image; 
 (i) repeating steps (a)-(h) until the desired image is printed on the substrate; and 
 wherein the encoder pattern includes a leading object and a lagging object, and wherein the target position is calculated based on a distance between the leading object and lagging object, a width of the printhead, and a scalar value determined by the number of passes used to print each band. 
 
     
     
       9. The scan printing method of  claim 8 , wherein the encoder pattern and the image are printed on the substrate with a printhead. 
     
     
       10. The scan printing method of  claim 8 , wherein the encoder pattern includes a plurality of objects. 
     
     
       11. The scan printing method of  claim 10 , wherein positions of the plurality of objects are mapped onto an image array of the sensor to calculate the target position and the projected moving distance of the substrate. 
     
     
       12. The scan printing method of  claim 8 , wherein the encoder pattern is printed on the substrate in an area outside of the printed band. 
     
     
       13. The scan printing method of  claim 8 , wherein the encoder pattern is part of the band of the image on the substrate. 
     
     
       14. The scan printing method of  claim 8 , wherein the encoder pattern includes magnetic marks. 
     
     
       15. The scan printing method of  claim 8 , wherein the encoder pattern includes electrically conductive marks.